MXPA02009674A - Maintenance of oil production and refining equipment. - Google Patents

Abstract

The deposition of asphaltenes and or petroleum waxes can be inhibited and or asphaltenes and or petroleum waxes can be removed from a well, pipe or vessel by contacting the asphaltene and or petroleum wax or the well pipe or vessel adjacent a location where deposition of asphaltene and or petroleum wax is expected, with a solvent including at least one compound of the formula (I): R1 (AO)n OOC (CH2)m Ph (R2)p where R1 is a C1 to C20 hydrocarbyl group; AO is an alkyleneoxy group and may vary along the (poly)alkyleneoxy chain; n is 0 or from 1 to 100; m is 0, 1 or 2; and Ph is a phenyl group, which may be substituted with groups (R2)p where each R2 is independently a C1 to C4 alkyl or alkoxy group; and p is 0, 1 or 2, and subsequently removing the solvent with softened, dissolved or dispersed asphaltenes and or petroleum waxes from the well, pipe or vessel.

Description

MAINTENANCE OF FACILITIES FOR THE PRODUCTION AND REFINEMENT OF OIL FIELD OF THE INVENTION The present invention relates to the elimination of deposits in oil production and refining facilities and, in particular, is related to the elimination of deposits of asphaltenes and / or petroleum wax from such installations.

BACKGROUND OF THE INVENTION Crude oil is a mixture of many components that varies depending on the origin. Normally, it will include components of a relatively low molecular weight, mainly hydrocarbons, including aliphatic and aromatic compounds. From these components, relatively low molecular weight products are obtained, such as naphtha, gasoline, oil, diesel or light fuel oil, benzene and toluene. Normally, crude oil also includes materials that have much higher molecular weights, including those known as asphaltenes and petroleum waxes. Asphaltenes vary depending on the origin of the oil, but are usually polycyclic compounds, usually aromatic or partially aromatic, including heterocyclic compounds especially with N and S atoms, and usually with chains of multiple aliphatic substituents. With probability, asphaltenes are not truly soluble in most crude oils, but are present as fine particles or lamellae. Its dispersion in oil is facilitated by the presence of resinous materials, usually called maltenes, and by the relatively high temperatures in most oil producing formations. Oil waxes are long-chain aliphatic compounds, usually C15 to Cioo and the general chain of mainly open. They are usually defined as paraffins and can be straight or branched chain materials. Normally, they are soluble in crude oil, particularly at the temperatures found in most petroleum-producing formations. In refining, the normal fate of these materials is their cracking to lower molecular weight compounds that then form part of useful fractions in the products, for example, petroleum waxes can be converted to alkanes or chain alkenes more short and that are useful, or end up as unrestrainable residues of crude oil, for example, as part of bituminous products. During production and processing and, in particular, at temperatures below those found in the oil producing formation, asphaltenes and petroleum waxes can be separated from the bulk of the oil and may become solidified as deposits on the surfaces with the which come into contact. These deposits can block the well or other pipes through which the oil passes, or they can be deposited in the bottom of separation vessels or storage tanks during production and early stages of refinery operations. It is important to eliminate such deposits to avoid blocking pipes and reducing the capacity of the containers. To separate both asphaltenes and petroleum waxes from pipes and vessels, aromatic solvents, such as xylene, are conventionally used, sometimes in combination with dispersants. Said aromatic materials are good solvents, but environmental considerations are leading to compelling to reduce the proportion of such volatile aromatic compounds used in industrial applications.

DETAILED DESCRIPTION OF THE INVENTION The present invention is based on the discovery that certain esters, particularly alkyl, of aromatic carboxylic acids, in particular benzoic acid, are very effective solvents for the materials deposited in oil recovery and refining facilities, in particular asphaltenes and petroleum waxes, and from the environmental point of view are much less objectionable than the xylenic solvents currently used for said purpose. In consecuense, the present invention provides a method for eliminating or preventing or inhibiting the deposition, in a well, pipe or container, of asphaltenes and / or petroleum waxes, characterized in that it comprises contacting the asphaltene and / or the petroleum wax, or the well, pipe or container, in a position adjacent to a point where the deposition of asphaltene and / or petroleum wax can be expected, with a solvent including at least one compound of formula (1): R1 - (A0) n - OOC ~ (CH2) m - Ph - (R2) p (I) wherein R1 is a Ci to C20 hydrocarbyl group, in particular a C3 to Cis alkyl or alkenyl group; AO is an alkyleneoxy group, in particular an ethyleneoxy or propyleneoxy group, and can vary along the (poly) alkylenoxy chain; n is 0 or is from 1 to 100, conveniently 0; m 0, 1 or 2, conveniently 0; and Ph is a phenyl group which may be substituted with groups (R2) P wherein each R2 is independently an alkyl or Ci to C4 alkoxy group; and p is 0, 1 or 2, conveniently 0; and subsequently separating, from the well, pipe or container, the solvent with the asphaltenes and / or petroleum wax softened, dissolved or dispersed. In the compound of Formula (I) used in the invention, R 1 may be an alkyl or alkenyl group.

The alkyl groups have the advantage that they are more stable, in particular to oxidation, than the alkenyl groups, but the alkenyl esters generally remain fluids at lower temperatures than the alkyl esters, especially in the case of chain materials. longer. Conveniently, an alkenyl group includes only a single double bond since the multiple unsaturation generally results in poor stability. In the separation of the asphaltenes, R 1 is in particular a relatively short chain, such as a C 2 to C 0 chain, for example an alkyl group of C 3 to C 6. Conveniently R1 is branched, for example, it is a group isopropyl (prop-2-yl), sec-butyl (but-2-yl), isobutyl (2-methyl-prop-1-yl), tert-butyl and / or 2-ethylhexyl, to reduce the ease with which the ester can be hydrolysed. In this regard, esters with secondary alcohols are particularly useful and, thus, R1 is especially a C3 to C5 secondary alkyl group and very conveniently an iso-propyl group. Another relatively short chain of alkyl ester which may be used includes ethyl, nonyl, and another linear chain of alkyl bonzoates such as propyl, butyl, pentyl and hexyl benzoates. An advantage derived from the relatively short chain esters is that they have a low viscosity. In the separation of petroleum waxes, the longer chain esters may be desirable to improve the low temperature solubility of the waxes in the solvent. Thus, R1 may be a C6 to C20 alkyl or alkenyl group, in particular C8 to Cie, which may be straight or branched chain, for example, as a mixture of esters such as benzoate (mixtures of C? 2 alkyl / C? 3), or branched, such as a 2-ethylhexyl or iso-nonyl, or branched chain C y alkyl, for example, as in the case of iso-stearyl (in fact a mixture of C? To C22 alkyls mainly branched with an average chain length close to C? 8). The longer, unsaturated chain groups include oleyl. When groups of longer chain length are used, in particular with a greater length of C 2, it is convenient that they are branched and / or unsaturated or include branching and / or unsaturation, since these promote liquid esters when the compounds of saturated linear chain esters can be solid and thus more difficult to use. Although the carboxylic acid used in the ester can be a dihydrocinnamic acid or a phenylacetic acid, it is very conveniently a benzoic acid, that is, conveniently m is 0. Similarly, although the phenyl ring of the acid may be substituted, it is convenient which is unsubstituted, ie, conveniently p is 0. The esters used in the invention can include a (poly) alkyleneoxy (AO) n chain in the formula (I), between the carboxyl group and the group and the R1 group. When the (poly) alkylenoxy chain is present, it is conveniently a (poly) ethyleneoxy (poly) propyleneoxy chain or a chain that includes both ethyleneoxy and propyleneoxy residues. In general, it is convenient not to include said chain in the ester, that is, conveniently n is 0. In particular, for the dissolution of asphaltenes, an especially useful ester is iso-propyl benzoate and the invention specifically includes a process in which the solvent is or includes iso-propyl benzoate. Isopropyl benzoate has a combination of properties that make them exceptionally useful in terms of their solvent role. As a pure material, it has a wide range of liquefaction with a high boiling point (eg 219 ° C approximately) and remains fluid at temperatures below the normally expected environmental temperatures (critical flow temperature <-60 ° C); has a flammability temperature (around 99 ° C) so that it is classified as non-flammable and, under normal conditions of use, has a low vapor pressure; has a density similar to that of water (1,008 kg.l "1 to 25 ° C), and a low viscosity (2,32 cSt at 25 ° C), measured by the U tube method, equivalent to 2, 34 mPa s) By comparison other alkyl benzoates have viscosities (at 25 ° C) as follows: ethyl benzoate: 1.9 cSt; 2-ethylhexyl benzoate: 6.1 cSt; nonyl benzoate: 7.5 cSt; '' benzoate (mixtures of Ci 2 / C 3 alkyl): 14 cSt and iso-stearyl benzoate: 30 cSt To achieve a solubility balance for both asphaltene and petroleum wax, mixed esters having a variety of R 1 groups may be convenient, or mixtures of compounds of formula (I), by providing a combination of dissolving properties that match the combinations of asphaltenes and waxes, said mixed esters or mixtures may have the additional advantage that they are more liquid than the pure saturated compounds, especially linear, of a similar total number of carbon atoms R1.

The solvent used in the process of the invention may consist entirely of one or more compounds of formula (I), or may contain other solvents in admixture. While xylenes may be included, xylenes or other solvents that include a substantial proportion of aromatic hydrocarbons are unlikely to be used as a major component of any mixed carrier fluid, as a consequence of their adverse impact on the environment. Mixtures with liquid paraffinic solvents may improve the solubility of petroleum waxes, but they are likely to reduce the solubility of asphaltenes. Other solvents such as water-soluble alcohols can be included, either as carrier fluids for additives (see below) or to improve, in practice, compatibility with aqueous materials. In such mixed solvents, the proportions used will depend on the particular nature of the material deposited in the pipe or container and, probably, on the balance and detailed composition of asphaltenes and waxes. When mixtures are used, the compounds of formula (I) will usually be present in an amount of at least 25%, usually at least 40%, more generally at least 50%, conveniently at least 60% and particularly at least 75%, by weight of the total carrier fluid used. When present, the other solvent components will be conveniently used at a level of usually 1 to 75%, usually 1 to 40%, more conveniently 2 to 25% and particularly 5 to 15% by weight of the total carrier fluid used. To facilitate the dispersion of asphaltene and / or petroleum wax, the solvent may include dispersants, in particular non-ionic surfactants and dispersants such as alcohol alkoxylates; reaction products between polyisobutylenuccinic anhydrides (PIBSA's) and alcohol alkoxylates, in particular ethoxylates of Cι to Ci8 alcohols, for example, C 3 to C 5; reaction products between PIBSA's and alkanolamines such as di- and tri-ethanolamine; and esters of sorbitan fatty acids, especially monoesters and in particular esters of unsaturated fatty acids, for example, sorbitan mono-oleate; sulfonic acid dispersants such as alkylarylsulfonic acids; or resinous dispersants such as dispersants based on phenol-formaldehyde resins and ethylene / vinyl acetate co-polymers. When dispersants are used, they will usually be included in an amount of 1 to 40%, more generally 1 to 30% and conveniently 1 to 20%, by weight of the solvent formulation. Other additives such as anti-fluid loss agents may be included in the solvent formulation used in the invention, particularly synthetic polymers such as polyacrylamides, polyacrylates, polyamides and similar polymers (some of which may also function as viscosity improvers).; corrosion inhibitors, demulsifiers; inhibitors of scale formation, oxygen scavengers; and other similar additive materials. Particularly, when such other additives are used, one or more co-solvents, for example, a water-soluble alcohol, such as propanol, can be employed, particularly for use in systems operating in the presence of water, and / or can be included a dispersant for the additive. In general, in production wells, the temperatures of the oil-bearing and crude oil formation are usually above room temperature, usually within the range of 50 to 150 ° C, in particular 60 to 120 ° C. Asphaltenes and / or waxes tend to be deposited at temperatures below the formation temperatures, but generally within or somewhat below the ranges indicated above, particularly in the range of 40 to 110 ° C. The compounds of formula (I), in particular iso-propyl benzoate, are better solvents for such materials at said moderately elevated temperatures. In this way, it may be convenient to operate at a temperature above the ambient temperature, for example, by heating the solvent, either deliberately or, for example, in an oil well by contact with the rock formations at elevated temperatures, in order to improve the behavior of the solvent . The temperature of the pipes, tanks and refinery installation will generally be determined according to the desired operating temperatures (often related to the temperature of the feed). The treated facility may consist of pipelines such as "the existing pipes within the structures of the oil wells, including the inner core of the well casings, pipelines, including the pipes of the casing headers, underwater pipelines and pipelines in refineries; or containers such as oil separators (to separate gas, oil-water and resinous phases); storage tanks, in particular near the head of the casing and in or near refineries; and refinery facilities. The separation of the deposits of asphaltenes and / or waxes can be carried out by means of the introduction of a mass of solvent in contact with the deposit, if necessary providing circulation or agitation of the solvent, then removing from the installation the softened, dissolved deposit or scattered. In storage tanks and in other points of the refinery process, the use of solvents to eliminate the existing funds in the tanks has the advantage that it is not necessary to open the tank to carry out a mechanical cleaning. The contents of the tank, the bottom of the tank and / or the solvent can be heated to facilitate solubilization and the tarry solid residues present in the tank can be dispersed in the solvent and normally added to a stream of crude oil for further processing in the tank. refinery The invention includes a process for the treatment of a petroleum storage tank, vessel or oil refinery pipe to remove deposits of asphaltenes and / or petroleum waxes, wherein a treatment material including a compound of formula (I) as defined above, it is introduced into the tank, vessel or pipeline in or adjacent to the location of an asphaltene and / or petroleum wax tank, after which the asphaltene is separated from the tank, vessel or pipeline and / or oil wax that has softened, dispersed or dissolved. Particularly, in oil wells, conventional techniques include the preventive application of solvents, optionally including dispersants, in order to avoid flocculation and deposition of asphaltenes and / or waxes. These methods generally comprise a continuous treatment by pumping the treatment material down the well, for example, using a capillary effect conduit, or by a slipstream, Thus, a thin layer of treatment material remains in the area. where it is considered that the presence of the deposition is probable and thus flocculation and deposition in the conduits and flow lines can be efficiently avoided. These methods are less effective in preventing deposition near the borehole area, for example, within the exploitation formation itself. In such cases, it is necessary to place the treatment material in the formation where it can inhibit the deposition of solids, for example, by compressing the treatment material into the formation. Accordingly, the invention includes a method of treating an oil well to remove a deposit of asphaltenes and / or petroleum waxes, wherein a solvent including a compound of Formula (I) as defined above, is the oil well in or adjacent to a deposit on a surface or in a rock formation. The invention further includes a method of treating an oil well to inhibit or prevent the deposition of asphaltenes and / or petroleum waxes, wherein a stream of a treatment material that includes a compound of Formula (I) as defined previously, it is introduced into the oil well in a position, particularly on a surface or in a rock formation, where the presence of said deposition can be expected, thereby eliminating the asphaltenes and / or petroleum waxes before they are deposited on said surface or in the formation. The following Examples illustrate the invention. All parts and percentages are by weight unless otherwise indicated.

EXAMPLE 1 Scampton C4 crude oil was added to hexane to precipitate asphaltenes (hexane dissolves the resins that stabilize the asphaltenes), the upper solvent layer was removed and the residual hexane was allowed to evaporate to obtain asphaltene as a viscous liquid residue. 5.2 g of iso-propyl benzoate-based solvent was added to 0.048 g of asphaltene and, after a few minutes at room temperature, the total asphaltene practice had dissolved (a few very small asphaltene particles remained visible in the solution) . The estimated (minimum) solubility was calculated to be approximately 0.85% by weight.

Example 1 In a separate experiment, it was carried out as described in Example 1 and this solubility is assessed in the various solvents as described in Example 1. The solvents ethyl benzoate, iso-propyl benzoate, benzoate 2- ethylhexyl, nonyl benzoate were mixed at 3: 1 by weight of iso-propyl benzoate and nonyl benzoate, benzoate (C12 / C13 alkyl mixture) and iso-stearyl benzoate. In each case the majority of the dissolved asphaltene but a few very small particles remained visible in the solution.

EXAMPLE 2 Approximately 0.025 g of asphaltene (obtained as described in Example 1) was applied by rubbing on a sample of rectangular mild steel of 5 cm x 1 cm and of known weight, and the sample was placed inside a jar of Also known weight crystal which was then weighed again to determine the amount of asphaltene by difference. Approximately 2 ml of solvent (accurately weighed) were added, the jar was sealed and placed on moving rollers, so that the metal sample was constantly covered with solvent at room temperature for about half an hour. The asphaltene was completely separated from the metal sample, indicating a minimum effective solubility of the asphaltene in the 1.3% solvent. Similar results were obtained using xylene as solvent.

Example 2a In a separate experiment, Example 2 was repeated using the solvents listed in Example la. In each case, the solvent separated all the asphaltene from the metal sample.

Example 3 Example 2 was repeated using about 0.18 g of asphaltene and about 0. 5 ml of iso-propyl benzoate. Again, the solvent separated all the asphaltene from the metal sample.

Example 3a In a separate experiment, Example 3 was repeated using different amounts: 0.4 g of asphaltene and 1 ml of the solvent, and the solvents listed in Example la. In each case, the asphaltene was removed at the end of the roller, but small traces adhered to the left of the metal surface. The cast residues were not measured quantitatively, but a visual inspection of the metal samples suggests that the classification of the solvents in this test is (from best to worst): ethyl benzoate > nonyl benzoate > 2-ethylhexyl benzoate > mixture of isopropyl benzoate and nonyl benzoate at 3: 1 by weight > iso-propyl benzoate > benzoate (C12 / C13 alkyl mixture) > isostearyl benzoate.

Example 4 The solubility of soft white paraffin wax (m.p. 49-59 ° C) in isopropyl benzoate was measured. At room temperature, the solubility of the wax was low (less than 1%), but after heating to 50-60 ° C it was possible to dissolve more than 60% by weight (with respect to the solvent) of the wax.

Example 4a In a separate experiment, Example 4 was repeated to assess the solubility of soft white paraffin wax in the solvents listed in Example la. In each case the solubility appears below room temperature but at 60 ° C more than 60% by weight of the wax in the solvents could dissolve.

Example 5 Metal samples of known weight were coated with the wax described in Example 4 by rubbing the soft paraffin on the surface of the sample and then assayed for the separation of wax by iso-propyl benzoate. using the method described in Example 2. The amount of wax was about 10% by weight of the solvent. At room temperature, a small amount of wax was separated giving a cloudy solution, but at 59 ° C all the wax easily separated from the surface of the sample.

Example 5a In a separate experiment, Example 5 was repeated using the solubility of soft white paraffin wax and the solvents listed in Example la. The solvents were removed from all waxes at room temperature from a cloudy solution. Visual inspection of elongated turbidity samples suggests that the classification of the solvents in this test is (from best to worst): iso-stearyl benzoate isostearyl benzoate > Nonalyl benzoate ~ 2-ethylhexyl benzoate > ethyl benzoate ~ isopropyl benzoate; mixture of iso-propyl benzoate and nonyl benzoate 3: 1 by weight.

Claims (10)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property: 1. A method to separate or prevent or inhibit deposition, in a well, pipeline or container, of asphaltenes and / or petroleum waxes, characterized in that it comprises contacting the asphaltene and / or the petroleum wax or the well, pipe or container, in a position adjacent to a point where the deposition of asphaltene is expected. and / or petroleum wax, with a solvent including at least one compound of formula (1):
2. X - (AO) n - OOC - (CH2) m - Ph - (R2) (I. where
3. R1 is a hydrocarbyl group Ci to C20; AO is an alkylenoxy group, and can vary along the (poly) alkylenoxy chain; n is 0 or is from 1 to 100; m 0, 1 or 2, and Ph is a phenyl group which may be substituted with groups (R 2) P wherein each R 2 is independently an alkyl or Ci to C 4 alkoxy group; and p is O, 1 or 2; and subsequently separating, from the well, pipe or container, the solvent with the asphaltenes and / or petroleum wax softened, dissolved or dispersed. 2. The method according to claim 1, wherein m, n and p are all 0. 3. The method according to claim 1 or 2, wherein R1 is a C3 to C5 branched alkyl group.
4. 4. The method according to any of claims 1 to 3, wherein the solvent is or includes iso-propyl benzoate
5. 5. The method according to claim 2, characterized in that R1 is a branched C8 to C20 alkyl or alkenyl group and / or unsaturated
6. 6. The method according to any of claims 1 to 5, wherein the asphaltene and / or the petroleum wax is brought into contact with the solvent at a temperature above ambient
7. 7. The method according to any of claims 1 to 6, wherein the solvent includes a dispersant for the asphaltene and / or petroleum wax
8. 8. The method according to any of claims 1 to 7 for the treatment of an oil storage tank, vessel or pipeline. of an oil refinery, to remove deposits of asphaltenes and / or petroleum waxes, characterized in that a solvent including a compound of formula (I) as defined above, is introduced into the tank, or pipe in or adjacent to the location of a deposit of asphaltene and / or petroleum wax, and then separated from the tank, vessel or pipe, the asphaltene and / or petroleum wax that has softened, dispersed or dissolved. The method according to any of claims 1 to 7 for the treatment of an oil well for the purpose of separating a deposit of asphaltenes and / or petroleum waxes, characterized in that a solvent including a compound of formula (I) as mentioned above, is introduced into the oil well in or adjacent to a reservoir on a surface or in a rock formation and then separates, from said surface or formation, the asphaltene and / or petroleum wax that is It has softened, scattered or loosened. The method according to any of claims 1 to 7 for the treatment of petroleum for the purpose of inhibiting or preventing the deposition of asphaltenes and / or petroleum waxes, characterized in that a stream of a solvent including a compound of formula (I) ) as defined above, is introduced into the oil well at a location, particularly on a surface or in a rock formation, where the presence of the deposition can be expected, thereby eliminating the asphaltenes and / or petroleum waxes before they are deposited on said surface or in said formation.